1：在你sdk安装的目录里面找 flex-sdk-description.xml 
2：在FLEX的命令行里面输入mxmlc -version 回车 
3：通过代码： 
  
<?xml version="1.0" encoding="utf-8"?> 
<!-- http://blog.flexexamples.com/2008/10/29/determining-your-flex-sdk-version-number/ --> 
<mx:Application name="mx_internal_VERSION_test" 
        xmlns:mx="http://www.adobe.com/2006/mxml" 
        layout="vertical" 
        verticalAlign="middle" 
        backgroundColor="white"> 

    <mx:Label text="{mx_internal::VERSION}" />  

</mx:Application>